IDENTIFICATION OF A GENE, SPOIIR THAT LINKS THE ACTIVATION OF SIGMA(E) TO THE TRANSCRIPTIONAL ACTIVITY OF SIGMA(F) DURING SPORULATION IN BACILLUS-SUBTILIS

Sporulation of Bacillus subtilis requires the coordinated expression of two separate developmental programs in the mother cell and forespore compartments by sigma(E) and sigma(F), respectively. This coordination is maintained through the action of cross-regulatory factors that control the activities of the various sporulation-specific sigma factors. We present here the isolation and characterization of of one such cross-regulatory factor, the spoIIR gene. Using a genetic screen, we have isolated four mutant alleles of spoIIR. These mutants were isolated as expressing sigma(F)-directed genes but not sigma(E)-directed genes. The block in sigma(E)-directed gene expression in spoIIR mutants was caused by an inability to process pro-sigma(E) to its active form. Cloning and characterization of the spoIIR gene determined that its transcription is directed by sigma(F). Thus, SpoIIR is required for linking the activation of sigma(E) to the activation of sigma(F) and coordinating the initiation of the two developmental programs required to form a spore.